The invention relates to a device for the selective galvanic coating of electrically conductive objects which are guided in a continuous or discontinuous manner past a rod-like anode. The rod-like anode is provided in its cross section with one or several edges. The objects are selectively coated by bringing them into contact with an electrolyte distributed on an electrolytic carrier.
Metallic strip products for use in the electronics industry, such as contact pins, contact springs or contact bands must be coated galvanically, preferably in a partially coated manner. This coating is especially important for noble metals in order to improve their electric properties, hardness or wear resistance for contacting important points.
This type of coating usually takes place by means of stationary or movable diffusion masks as described e.g. in U.S. Pat. Nos. 4,132,617; 4,425,212; WO-OS No. 87/02 076 and DE-OS No. 29 28 904. The production cost and the equipment cost of the marking technique is very high and expensive. Electrolyte losses due to it being drained off the outside of the apparatus are difficult to avoid. Furthermore, it is difficult to maintain the required tolerances, which are a function of the temperature change, deformation or changes in length. Maintenance of these factors, and thus maintenance of the required tolerance, is either not assured or only assured to an unsatisfactory extent.
U.S. Pat. No. 4,610,772 and EP-OS No. 1 154 795 teach methods of coating electrically conductive objects in which the objects to be selectively coated are guided past anodically connected, rotating rollers. The rollers are provided with coatings of adsorbent fabrics. The roller is immersed in the electrolyte or the roller is otherwise supplied with the electrolyte solution.
The transfer of the metal onto the objects takes place by bringing the metallic objects in contact with the fabric impregnated with electrolyte. A disadvantage of this is an insufficient definition and insufficient evenness of the layers. In most instances, additional masking or adhesive must be used in order to protect areas which are not to be coated.
U.S. Pat. No. 4,452,684 describes a method in which the objects are guided past a stationary, porous body and the electrolyte is supplied via a hollow shaft. Uneven separations and layer thicknesses likewise result on account of the loading on all sides with electrolyte.
DE-PS No. 37 30 740 teaches a method for the selective, galvanic coating of objects guided in a continuous manner past an anode. The coating takes place by means of bringing the objects in contact with an electrolytic carrier on which the electrolyte is distributed. The electrolytic carrier has defined edges and the electrolyte is applied over a level surface thereof. The carrier is connected to the anode and is put into mechanical oscillations. The coatings are not sufficiently contour-defined here for specialized applications.